Hello everyone,
I have one doubt regarding voltage divider circuit. I am using two battery cells of 3.7v each connected in series. To make the voltage less for arduino , I am using one voltage divider circuit. In that , the resistors(R1 , R2) both are of equal resistance i.e; 220K. The voltage I am getting from this circuit is 3.7v. But when I am making a connection with arduino board, the voltage is measured as 0.6/ 0.7 v.
Why this is happening? How i'll be able to power up arduino with this successfully?
I am attaching some photos of connections.
Please inform in case you don't get something.
Thank you.
A voltage divider is the wrong way to lower the voltage to drive the arduino. Think of the arduino as a resistor that varies resistance when it for examples is instructed to light up an LED or close a relay. You need some kind of low voltage drop voltage regulator otherwise you will never be able to get a fairly constant voltage for your arduino.
Why don't you use the built in voltage regulator and connect the full ~7.4V to the DC jack input already available on your arduino?
Ok . I get it. Thank you so much.
I have one more added doubt to your last suggestion. If i'll use the DC Jack to power up the arduino then how can I measure the voltage of battery connected to it? I don't know much about it but i know that to get the battery voltage you need to connect the battery to analog pin and GND of arduino.
Then how can I measure the voltage of battery by connecting the it to DC Jack of arduino.
Please suggest some ideas.
Thank You
The ground should be common so the ground of the battery pack is the same as GND on the arduino. You can use the voltage divider you first described to measure the cell voltage of the FIRST cell in the pack, but if you add a resistor of roughly the same value as both you have right now (440k) the second cell voltage can also be measured. If you use 440k the maximum voltage of all cells in series can be 10V.
I can not tell you (without doing the math myself) what the A/D values of each cell will be when fully charged and it also depends a little bit on the "440k-resistor". If you use something closer to 380k the maximum voltage of the battery pack must be a lot lower than 10V otherwise you risk frying the analog input of your arduino. it is important to do the math first and also to make a measurement with a digital multimeter BEFORE you connect the A/D inputs.
